Second-calendar year Baltic Gulls have a different primary moult strategy to the same age Lesser Black-backed Gulls (graellsii and intermedius). Most Baltic Gulls moult during their time in their winter quarters and so arrive back in Europe with a fresh set of second-generation primaries. In contrast Lesser Black-backed Gulls moult their primaries in September. So basically second-calendar Baltic Gull is identifiable on primary moult timing. There are no known photographs of either graellsii or intermedius with a full set of second-generation primaries as early as July. Therefore I feel confident to call this gull a Presumed Baltic Gull. Presumed because it doesn't have a nice colour-ring from a Baltic Gull breeding colony. It may prove acceptable without the ring, but time will tell on that score.
Thanks for looking.